Introduction:Fluorescent semiconductor nanoparticles, also known as quantum dots (QD’s), are excellent candidates for fluorescent labels for detection invitro and in vivo.1 They exhibit superior resistance against photobleaching compared to organic dyes and the possibility for tailor-made functionalization. Recently, our lab has developed a method for the synthesis of fluorescent silicon nanoparticles.2 These particles display very little toxicity in cells and have shown interesting optical properties. Si NPs are synthesized via the reduction of silicon tetrachloride in a reverse micelle system. The particles are nearly monodisperse with a size distribution of 1.57 ± 0.22 nm (see abstract Loes Ruizendaal). The initial hydrogen terminated silicon surface is passivated with organic moieties for the prevention of oxidation and the addition of functional groups. Next to alkyls, Si NPs have been synthesized with amines, azides and acid functionalities. The functionalities also influence the optical and solubility properties.

Goal:

The goal of my project is to incorporate the Si NPs as fluorescent labels in multiplex diagnostic systems. These applications acquire Si NPs that are conjugated easily with various active natural compounds. The first part of this project is to synthesize and characterize Si NPs with functional shells for further conjugation.

For multiplex measurements, Si NPs that emit on different wavelengths are required. Up to now, we are able to produce one type of Si NPs which emit light high in the UV region. In this project, new methods for the synthesis and isolation of Si NPs with emission maxima at other wavelengths, more towards visible light, will be developed. The emission of the Si NPs is size dependent, with bigger particles emitting at higher wavelengths.

With the multiple color Si NPs, multiplex diagnostic assays can be designed for the detection of toxins. The different Si NPs can be addressed to different toxins, which makes the detection of multiple toxins in one sample possible. A nice example for such an assay is developed by Goldman et al.3, where four different quantum dots are addressed to four different toxins. With the deconvolution of the fluorescence spectra, the amount of toxin in the sample can be quantified.